The present invention relates to a coordinated lift system and, more particularly, to a coordinated lift system incorporating at least two lift mechanisms that communicate by wireless signals on user selected RF channels to coordinate lift mechanisms in the raising and lowering of a vehicle.
The need to lift a vehicle from the ground for service work is well established. For instance, it is often necessary to lift a vehicle for tire rotation or replacement, steering alignment, oil changes, brake inspections, exhaust work, and other automotive maintenance. Traditionally, lifting a vehicle has been accomplished through the use of equipment that is built-in to the service facility, such as either lift units with the hydraulic actuator(s) installed below the surface of the floor or two and four post type lift systems installed on the floor surface. These built-in units are located at a fixed location at the service facility and adapted to engage the vehicle frame to lift the vehicle from the ground. However, built-in units tend to be relatively expensive and are sometimes not as useful as they might otherwise be due to their immobility.
In an effort to increase the versatility and mobility of lift devices and reduce the need to invest in permanently mounted lifting equipment, devices commonly known as a mobile column lifts (MCL's) have been developed. Apparatus for lifting a vehicle using multiple MCL's is described in U.S. Pat. No. 6,315,079 to Berends et al. The lifting device in the Berends patent includes using a number connecting lines or wires to provide electrical power and control of the MCL's. The lines or wires that are connected between the MCL's allow the vehicle to be raised or lowered in a coordinated fashion. However, the lines and wires used to connect the MCL's extend across and are looped within the working area. The presence of the wires and lines in the work area poses a hazard to people working near the vehicle, and the connecting lines may be damaged by vehicles driving over them.
Another apparatus for lifting a vehicle using multiple MCL's is described in U.S. Pat. No. 6,634,461. The '461 lifting device includes multiple MCL's that are coordinated by coded wireless signals, such as RF (radio frequency) signals, and powered by rechargeable batteries in each lift unit. By these means, the lifting devices in the '461 patent eliminate the need for both power cables and control cables. However, the wireless system of '461 does not allow the user to select the frequency of operation of transceivers of the control units of the lift devices. For this reason, two systems may not be usable simultaneously in a given location without the possibility of interference. Further, if signal interference occurs at a specific location, the frequency on which the system is operating cannot be changed in the field to avoid such interference.
Accordingly, there remains a need for a control unit for a wireless mobile lift system with intercommunication frequencies which can be user selected in the field to avoid interference from other lift systems or from unknown sources.